Virtual memory is an abstract concept of memory that a computer system uses when it references memory. Virtual memory consists of the computer system's main memory (RAM), which at the present state of the art is DRAM, its file systems and paging space. At different points in time, a virtual memory address referenced by an application may be in any of these locations. The application does not need to know which location as the computer system's virtual memory manager (VMM) will transparently move blocks of data around as needed.
Power consumption has become a significant factor in the operational costs of computer data centers. The information systems industries have continuously sought to reduce power consumption in data processing equipment. In recent years, it has been appreciated that even operational virtual memory, energy, i.e. power consumption, will have a significant effect on power consumption costs. Consequently, conventional virtual memory controllers now have the capability of putting DRAM memory portions into lower power consumption modes during idle states. Such conventional powering down approaches have involved significant enhancement of memory controller structure. Such memory controller enhancements, while effective in smaller systems have been found to be impractical for current larger multicore virtual memory systems.